Sprayable polymer membrane for agriculture

Abstract

A process for preparing a polymeric membrane for soil materials used in crop production comprising providing an aqueous dispersion of polyurethane and spraying the aqueous dispersion onto soil materials to be used in crop production to form a polymeric membrane.

Claims

1. A process for preparing a polymeric membrane for soil to be used in crop production, the process comprising: providing a sprayable aqueous dispersion of ionic polyurethane, wherein the aqueous dispersion further comprises a thickening agent; and spraying the aqueous dispersion onto an area of soil to be used in crop production from seeds or pre-grown plants to form a polymeric membrane on the surface of the area of soil, wherein the aqueous dispersion is sprayed onto the area of soil (i) prior to planting of the seeds in the area of soil, or (ii) prior to planting of the pre-grown plants in the area of soil, or (iii) after planting of the pre-grown plants in the area of soil.

2. A process according to claim 1, wherein the thickening agent is present in the aqueous dispersion in an amount in the range of from 1 to 20 weight %.

3. A process according to any claim 1, wherein the viscosity of the aqueous dispersion is no more than 200 milliPascal.Math.second (mPa.Math.s).

4. A process according to claim 1, wherein the thickening agent is selected from the group consisting of gelatine, alginate, wood meal, xanthan gum, polyacrylamide (PAM) and a cellulose.

5. A process according to claim 1 wherein the ionic polyurethane comprises ionic groups selected from the group consisting of carboxylate, sulfonate and ammonium.

6. A process according to claim 1, wherein the ionic polyurethane comprises the reaction product of (a) a diisocyanate; and (b) at least one active hydrogen containing compound, wherein at least one active hydrogen containing compound comprises an ionic group or an ionisable group which provides an ionic group on neutralisation.

7. A process according to claim 1, wherein the ionic polyurethane is derived from (a) reaction of a diisocyanate and a prepolymer comprising active hydrogen groups to form an isocyanate terminated prepolymer, and (b) reacting the isocyanate terminated prepolymer with a chain extender monomer comprising ionic or ionisable groups.

8. A process according to claim 1, wherein the ionic polyurethane comprises a polyol prepolymer of molecular weight of 500-10,000 Daltons.

9. A process according to claim 1, wherein the ionic polyurethane is biodegradable and comprises one or more units derived from a polyester polyol and an aliphatic diisocyanate.

10. A process according to claim 1, wherein the ionic groups of the ionic polyurethane are provided by (a) polymer-forming reactions with one or more monomers selected from the group consisting of 2,2-bis(hydroxymethyl) propionic acid (BMPA), tartaric acid, dimethylol butanoic acid (DMBA), glycolic acid, thioglycolic acid, lactic acid, malic acid, dihydroxy malic acid, dihydroxy tartaric acid and 2,6-dihydroxy benzoic acid and (b) neutralisation of the resulting polymer with a tertiary amine.

11. A process according to claim 1, wherein the polymeric membrane comprises cross-linked ionic polyurethane.

12. A process according to claim 11, wherein the aqueous dispersion further comprises a cross-linker selected from the group consisting of divalent and trivalent metal cations, wherein the cross-linker cross-links the ionic polyurethane to form the cross-linked ionic polyurethane.

13. A process according to claim 11, wherein the ionic polyurethane is cross-linked by using a slight excess of isocyanate when formulating the ionic polyurethane.

14. A process according to claim 1, wherein the ionic polyurethane is present in an amount of from 10 to 60% by weight of the aqueous dispersion.

15. A process according to claim 1, wherein the aqueous dispersion is sprayed onto the area of soil at a rate of from 100 to 1000 g polyurethane solids content per square meter of the area of soil.

16. A process according to claim 1, wherein the aqueous dispersion comprises urea.

17. A process according to claim 1, wherein the pre-grown plants are selected from the group consisting of seedlings and saplings.

18. A process according to claim 1, wherein the aqueous dispersion further comprises a pigment or coloring agent to suppress weed growth in the area of soil.

Description

EXAMPLES

Brief Description of Drawings

(1) Examples of the invention are described with reference to the attached drawings.

(2) In the drawings:

(3) FIG. 1 is a graph showing the cumulative water loss of the polymer of Example 1 applied to sandy soil as a spray in and mixture with raw latex and alginate in a weight ratio PU (Example 1):raw latex:alginate of 3:1:0.5 in accordance with Example 6.

(4) FIG. 2 is a graph showing the cumulative water loss with time for the polymer of Example 1 sprayed onto soils in the form of sand, loam and clay, as described in Example 7.

(5) FIG. 3 is a graph comparing the cumulative water loss with time from loam soil sprayed with the polymer of Example 4, as described in Example 8. The upper plot relates to the control and the lower plot to the Example 4 polymer.

(6) FIG. 4 is a graph showing the variation in viscosity with rotation speed described in Example 10 (b). The upper plot relates to the ratio of 1:0.1 the second from top plot to 1:0.05 and the lower plot to 1:0.01 as described in Example 10 (b).

(7) FIG. 5 is a graph showing the cumulative soil water loss with time for soil to which a spray of various polymers has been applied as described in Example 19. The top plot relates to the control. The second from top to Example 1 (5 g), the third from top to 2% Alg (alginate), the fourth from top the 8% Alg, the fifth from top 2% PAM and the bottom plot 2% XG (xanthan gum).

(8) FIG. 6 is a schematic drawing showing the furrow and irrigation pattern used in conducting the field trial referred to in Example 20.

(9) FIG. 7 is a graph showing biodegradation results from the trial reported in Example 23.

POLYMER SPRAYABLE FORMULATION

(10) The following polyurethane sprayable membranes may be prepared using the general procedures outlined below.

Abbreviations

(11) BMPA: 2,2-Bis(hydroxymethyl)propioninc acid DTAB: n-Dodecyltrimethylammoniumbromide EDA=Ethylenediamine BDO=1,4-butane diol MDEAN-methyldiethanol amine PUUPolyurethaneurea PU=Polyurethane Latex (Natural both crosslinked and Raw) PPG=Polyproylene glycol IPDIIsophorone diisocyanate PDMS=Polydimethylsiloxane polyol (Carbinol) SDDS=Sodium dodecyl sulffate AcOH=Glacial Acetic acid DBTL=Dibutyltin dilaurate PP=Prepolymer SSSoft segment HSHard segment CE=Chain extender SCMC: Sodium salt Carbomethoxy cellulose DICAPQ2020 Polyester polyol DMPA polyol HA-0135

(12) Test Procedure

(13) Particle size was measured by Wyatt Dyna Pro Plate Reader Wyatt Technology Corporation, 6300 Hollister Ave, Santa Barbara, Calif. 93117-3253. The viscosity of polymer solution was measured by Brookfield digital rotary viscometer, model 94800-0. GPC measurements of other polymers were performed on a Shimadzu system equipped with a CMB-20A controller system, a SIL-20A HT autosampler, a LC-20AT tandem pump system, a DGU-20A degasser unit, a CTO-20AC column oven, a RDI-10A refractive index detector and with 4 Waters Styragel columns (2*HT3, HT4, HT5 each 3007.8 mm) providing an effective molar mass range of 100-410.sup.6) and with N,N-dimethylacetamide (DMAc) containing 2.1 g.Math.L.sup.1 of lithium chloride (LiCl) as eluent with a flow rate of 1 mL.Math.min.sup.1 at 80 C. The molar masses in poly(methyl methacrylate) (PMMA) equivalents were obtained from a calibration curve constructed with low dispersity PMMA standards (Polymer Laboratories). A third-order polynomial was used to fit the log M.sub.p versus time calibration curve, which was approximately linear across the molar mass range from 1,020 to 1,944,00 g.Math.mol.sup.1.

(14) DSC was performed on a Mettler Toledo DSC821 using samples (5 mg weight) at a heating rate of 10 C./min under nitrogen purge. The samples were stored for 48 h under a vacuum at room temperature (RT) (0.1 Torr) prior to analysis. Tensile testing was performed on an Instron Model 4468 universal testing machine following the ASTM D 882-02 test method at ambient temperature (23 C.) with a humidity of around 55%.

(15) Materials

(16) Natural latex rubber (water emulsified, Sprayable Latex with 40.2% solids content was received from Barnes, Sydney).

(17) Sodium Alginate was received as powder from Melbourne Food Depot, Victoria.

(18) DICAP2020 Polyester polyol and DMPA polyol HA-0135 were received from GEP Speciality Chemicals and used after degasing and drying under standard procedure.

(19) Polymersas synthesised.

(20) General Method of Synthesis

(21) Polyol and CE were degased and dried under vacuum prior to use.

(22) Polymerisation reactions may be carried out by two step method in a N2 atmosphere in a constant-temperature oil bath using 250-mL round-bottom flask fitted with mechanical stirrer, thermometer, and condenser. PU reaction may be carried out by modified one step method.

(23) One Step Method

(24) Diisocyanate (IPDI) was weighed into a three neck RB flask equipped with overhead mechanical stirrer, dropping funnel and nitrogen inlet. A required amount of degassed polyol, diol chain extender, appropriate ionomer and DBTL catalyst (0.1 wt %) were added to the IPDI. The reaction was heated at 80 C. for 1 h and later at 90 C. for 2 h. The reaction mixture was then cooled down to 60 C. and the viscosity-reducing agent acetone and the neutralizer acid or base were subsequently added under stirring. After 30 mins, the reaction mixture was further cooled down to sub ambient temperature and deionised water containing surfactant was added to obtain a water dispersible polymer emulsion.

(25) Two-Step Method

(26) Appropriate amount of diisocyanate (IPDI) was weighed into a three neck RB flask equipped with overhead mechanical stirrer, dropping funnel and nitrogen inlet. The flask was heated in an oil bath at 70 C. The appropriate amount of degassed polyol was then added to IPDI. DBTL catalyst (0.1 wt %) was added to the reaction mixture after few minutes. The reaction mixture was then heated at 80 C. for 2 h. Pre-dried BMPA dissolved in anhydrous NMP solvent and added to the above pre-polymer quickly and reaction continued another 2 h at 90 C. The flask was then cooled down to 60 C. and with appropriate acid or base for 30 mins. The reaction mixture further cooled down to sub-ambient temperature and deionised water containing appropriate surfactant was added to obtain an emulsified prepolymer solution. Accurately weighed amine CE diluted in deionised water was added drop wise to this solution and stirring continued until NCO peak disappeared. The water dispersible polymer emulsion was then transferred to a screw tight container under nitrogen atmosphere and stored at ambient temperature. Other experiments with PUU index 1.01 and 1.03 were carried out under similar conditions.

Example 1: Anionic Polymer

(27) A mixture of PPG (MW 1000, 20.00 g) was degassed at 80 C. for 2 h under vacuum (0.1 torr). IPDI (8.22 g) was weighed into a three neck flask equipped with mechanical stirrer, dropping funnel and nitrogen inlet. The degassed polyol (10.0 g) was then added to IPDI followed by DBTL catalyst (0.03 g) and the flask was heated at 80 C. for 1 h with stirring. Pre-dried BMPA (0.43 g) dissolved in minimum amount of anhydrous NMP was added to the above pre-polymer quickly and reacted for another 2 h at the 90 C. The flask was cooled down to 60 C. and anhydrous Triethylamine (0.324 g) was added and reacted for 30 mins. The flask was further cooled down to 0 C. using an ice cold bath. Deionised water (44.0 mL) containing 2 wt % SDDS was added to this pre-cooled prepolymer mixture and was stirred vigorously to yield an emulsified opaque solution. Chain extension agent EDA (0.765 g) was then added drop wise to this solution and stirring continued for 30 mins. The reaction flask was later warmed to 25 C. and the stirring continued until the NCO peak disappeared. The low viscous stable water dispersible polymer emulsion thus obtained was stored in an air tight container at ambient temperature. The polymer showed an average particle size distribution of 42553 nm with a viscosity of 625 mPa.Math.s. The molecular weight of polymer was M.sub.n=117138, M.sub.w=699278 and PD=2.5.

(28) All other example's subsequent formulations also contained water containing 2-wt % SSDS surfactant.

(29) The above polymer solution can be crosslinked using 1-20% calcium chloride solution. The crosslinking is preferably carried out by spraying the calcium chloride solution on the soil bed prior to spraying PU solution.

(30) The polymer showed good membrane forming properties post spray on sandy soil at room temperature.

Example 2: Example 1 with Urea Powder

(31) The degassed polyol (20.0 g) was weighed into a three neck flask equipped with mechanical stirrer, dropping funnel and nitrogen inlet. Urea powder (0.6 g) was then added to the flask and stirred along with polyol at 70 C. for few mins. IPDI (8.22 g) was added into polyol and urea mixture followed by DBTL catalyst (0.030 g). After the addition, the reaction mixture was heated at 80 C. for 1 h with stirring under nitrogen. Pre-dried BMPA (0.43 g) dissolved in minimum amount of an anhydrous NMP was added to the above pre-polymer quickly and reacted for another 2 h at 90 C. The flask was cooled down to 60 C. and anhydrous Triethylamine (0.324 g) was added and reaction continued for 30 mins. The flask was further cooled down to 0 C. using an ice bath. Deionised water (44.0 mL) containing 2 wt % SDDS was quickly added to this pre-cooled prepolymer mixture and was stirred vigorously to yield an emulsified opaque solution. Chain extension agent EDA (0.765 g) was added drop wise to this solution and stirring continued for 30 mins. The reaction flask was later warmed to 25 C. and the stirring continued until NCO peak disappeared. The low viscous stable aqueous dispersion of polyurethanes thus obtained was stored in an air tight container at ambient temperature. The polymer showed an average particle size distribution of 333110 nm with a viscosity of 222 mPa.Math.s.

(32) The water dispersible polymer emulsion showed good membrane forming properties post spray on sandy soil at room temperature under controlled laboratory conditions.

Example 3: Example 1Higher HS (Hard Segment of Polymer)

(33) The synthesis procedure was identical to Example 1. The amounts of precursors used are as follows:

(34) IPDI=12.04 g, PPG=20.0 g, BMPA=0.87 g, Triethylamine=0.65 g, Deionised water=44.0 mL, EDA=1.57 g

(35) The emulsified polymer solution showed good membrane forming properties post spray on sandy soil at room temperature and showed number molecular weight M.sub.n=52411, and PD=2.2.

Example 4: Cationic Polymer

(36) IPDI (11.29 g) was weighed into a three neck flask equipped with mechanical stirrer, dropping funnel and nitrogen inlet. The degassed polyol PPG (20.0 g) and MDEA (3.14 g) and catalyst DBTL (0.1 wt %) were then added and the reaction continued for 1 h at 80 C. and 2 h at 90 C. The flask was cooled down to 60 C. temperature and glacial acetic acid (1.58 g) was added through a syringe and reaction continued for 30 mins. Anhydrous acetone (25.0 mL) was then added to polymeric mixture as a viscosity reducing agent and flask was cooled down to 0 C. using an ice cold bath. Deionised water (44.0 mL) containing 2 wt % n-Dodecyltrimethylammoniumbromide (DTAB) was added to this pre-cooled prepolymer mixture and was stirred to yield an emulsified opaque solution. Chain extension agent EDA (0.05 g) diluted in deionised water was added dropwise to this solution. After the addition, the flask temperature was warmed to 25 C. and stirring continued until NCO peak disappeared. The acetone was later removed and PUU emulsion was stored at ambient temperature.

(37) The water dispersible polymer emulsion showed good membrane forming properties post spray on loam soil.

Example 5: Pot Trial

(38) General Procedure for Preparing Polymer Blend

(39) For small volumes of PU blends, material, accurately weighed (+/0.1 g), was placed in a 100.0 mL Schott bottle and shaken vigorously for 30 seconds. The order was PU, latex, alginate. For larger quantities used in field trials, the same order was used and stirring carried out by use of a paddle or shaken in 5 L plastic containers.

(40) Various PU blends in different ratios with latex, with and without alginate, were prepared using this method.

(41) Method

(42) Small pot trials to determine soil water evaporation were carried out using metal pots with wire mesh bottoms which are packed with soil. (The pots are 105 mm diameter and 50 mm deep-soil is packed into the pot to a height of approximately 45 mm). Three types of soil have been trialed; sand, loam and clay. The surface of the soils are damped down with mist-sprayed water 5 g per pot using a mask to ensure the spray lands on the soil rather than the container. This is allowed to dry off overnight. The experimental PU is sprayed onto the pot surface using a mask and allowed to membrane form overnight. Treated pots are immersed in 2 cm of water allowing water to wick up and into the pot through the wire meshan untreated pot with the same soil is used to time the immersion. Pots are placed on electronic balances in a conditioned atmosphere room set at 30 C. and 40% Relative Humidity (RH). The time of trial varies from 4 to 10 days depending on the rate of evaporation.

Example 6

(43) Pot Trial of Polymer: Example 1:Raw Latex:Alginate (3:1:0.5) Blends on Sandy Soil

(44) The elastic water-based polyurethane blend was examined for water barrier properties on small pot trials. The formulation comprised of the Polymer composition of Example 1 with raw latex and alginate (2.5% solution) in the ratio3:1:0.5, showed significantly less water loss compared to control as shown in FIG. 1.

Example 7

(45) Pot Trial of Polymer: Example 1 on Different Soils

(46) Changes were made in carrying out laboratory trials with Loam and Clay soils to overcome soil cracking and pulling away from the side of pots to get consistent results. The method consists of crushing the dry soils to prepare a relatively flat surface and mist spraying with water. The pots were then allowed to dry overnight. This produced a soil with a closer representation of soils found in fields.

(47) Polymer (Example 1) alone was sprayed onto small pot trials with the above mentioned soil conditioning. Sand, loam and clay soils were trialed and the results are plotted in the graph presented as FIG. 2 in the drawings.

(48) Polymer (Example 1) alone was tested in small pot trials with the above mentioned soil conditioning using aqueous 2% CaCl.sub.2 solution crosslinker as a primer.

(49) Example 1 was also trialed on a primer of cross-linked Alginate.

Example 8

(50) Pot Trial of Cationic Polymer (Example 4)

(51) Polymer (Example 4) alone was sprayed onto small pot trials with the above mentioned soil conditioning on loam soil. The polymer provided 30% water reduction as shown in FIG. 3 of the drawings.

Example 9: Example 1, with Humus Coal

(52) The polymer solution prepared in Example 1 was mixed with 5 wt % solution of K-humtae-S90 in different ratio by gentle agitation at ambient temperature. The emulsified black polymer solution showed good film forming properties post spray on sandy soil at room temperature.

Example 10 (a): Example 1, with Viscosity Modifier Xanthan

(53) The polymer solution prepared in Example 1 was mixed with 2% Xanthan solution in various ratios (Table 1) by vigorous agitation for several minutes at ambient temperature. The emulsified polymer solution showed an increased viscosity and was sprayable. The polymer, upon spray, showed good film forming properties post spray on sandy soil at room temperature.

Example 10 (b) Example 1, with Viscosity Modifier Gelatine

(54) The polymer solution prepared in Example 1 was mixed with 2% Gelatine solution in various ratio (Table 2) by vigorous agitation for several minutes. The emulsified polymer solution showed an increased viscosity as shown in FIG. 4 and was sprayable. The polymer, upon spray, showed good film forming properties post spray with minimum wicking on sandy soil at room temperature compared to control (Table 2).

(55) It was found that the concentration of Gelatine gum mixture decreased with increasing value of spindle's rotation speed. Also, when higher ratio of xanthan gum to polymer was used, greater viscosity values were observed.

Example 10 (c): Example 1, with Viscosity Modifier Alginate

(56) The polymer solution prepared in Example 1 was mixed with 2-8% Alginate solution in various ratios (Table 3) by vigorous agitation for several minutes at ambient temperature. The emulsified polymer solution showed an increased viscosity and was sprayable. The polymer, upon spray, showed good film forming properties post spray on sandy soil at room temperature.

Example 10 (d): Example 1, with Viscosity Modifier Polyacrylamide

(57) The polymer solution prepared in Example 1 was mixed with 2% polyacrylamide solution in various ratios (Table 4) by vigorous agitation for several minutes at ambient temperature. The emulsified polymer solution showed an increased viscosity and was sprayable. The polymer, upon spray, showed good film forming properties film post spray on sandy soil at room temperature.

(58) TABLE-US-00001 TABLE 1 Wicking experiment and sprayability test results of Example 1 and xanthan gum mixtures Xanthan Gum Example 1 Conc. (wt/wt) comp. with:Xanthan Gum) Wicking Sprayability 2% 1:0.01 1.5 cm Sprayable 1:0.05 1 cm Sprayable 1:0.1 0.2 cm Sprayable 1:1 Unsprayable 2.2 cm Sprayable

(59) Likewise other viscosity modifiers showed similar results when mixed in different ratios with the Example 1. A comparison of different viscosity modifiers Gelatine, Alginate and PAM with Example 1 are summarised in Tables 2, 3 and 4 below.

(60) TABLE-US-00002 TABLE 2 Gelatine Example 1 Conc. (wt/wt) comp. with:Gelatine) Wicking Sprayability 2% 1:0.01 2.2 cm Sprayable 1:0.1 2 cm Sprayable 1:1 1.3 cm Sprayable

(61) TABLE-US-00003 TABLE 3 Alginate Example 1 Conc. (wt/wt) comp with:Alginate Wicking Sprayability 2% 1:0.1 2 cm Sprayable 1:0.75 1.5 cm Sprayable 1:1 1 cm Sprayable

(62) TABLE-US-00004 TABLE 4 PAM Example 1 Conc. (wt/wt) comp. with:PAM Wicking Sprayability 2% 1:0.01 1 cm Sprayable 1:0.05 0.3 cm Sprayable 1:0.1 Unsprayable 1:1 Unsprayable

Example 11: Example 1 with 64 wt % HS, PPG MW 974.2

(63) The synthesis procedure was identical to Example 1. The amounts of precursors used are as follows;

(64) IPDI=13.87 g, PPG=10.0 g, BMPA=1.397, Triethylamine=1.05 g, Deionised water=41.0 g, EDA=2.50 g

(65) The emulsified polymer solution showed good film forming properties post spray on sandy soil at room temperature and showed number molecular weight M.sub.n=52411, and PD=2.2

Example 12: Example 1 Prepared with PCL, MW 916.77

(66) The synthesis procedure was identical to Example 1. The amounts of precursors used are as follows:

(67) IPDI=16.53 g, PCL=40.0.0 g, BMPA=0.822 g, Triethylamine=0.69 g, Deionised water=88.20 g, EDA=1.47 g

(68) The emulsified polymer solution showed good film forming properties post spray on sandy soil at room temperature and showed number molecular weight M.sub.n=52411, and PD=2.2

Example 12a: Polymer Example 12:Raw Latex:Alginate (3:1:0.5) Blends

(69) The blend formulation of Example 12 with Raw latex and Alginate was prepared as described in Example 6.

Example 12b

(70) The composition of Example 12 was mixed with 5 wt % solution of K-humate-S90 in different ratios by gentle agitation at ambient temperature. The emulsified black polymer solution showed good film forming properties post spray on sandy soil at room temperature.

Example 13: Example 12 with 25 wt % HS

(71) The synthesis procedure was identical to Example 1. The amounts of precursors used are as follows; IPD=12.42 g, PCL=40.0 g, BMPA=0.327, Triethylamine=0.248 g, EDA=0.586 g, Deionized water 80.0 g.

Example 14: Example 1 with Mixed Polyol

(72) The process of Example 1 was repeated with a mixed polyol PPG and PPL.

(73) The synthesis was carried out using blends of both PPG and PCL in 1:1 ratio with same HS wt % composition. The emulsified polymer solution showed good film forming properties post spray on sandy soil at room temperature.

Example 15: Example 1 with DICAP Polyol, MW 1100

(74) The synthesis procedure was identical to Example 1. The amounts of precursors used are as follows; IPDI=16.23, DICAP=40.0.0 g, BMPA=0.927 g, Triethylamine=0.699, EDA=1.66 g, Deionized water 100.0 g. The emulsified polymer solution showed good film forming properties post spray on sandy soil at room temperature.

Example 16: Example 12 with DICAP and PCL Polyol Blends

(75) The synthesis of Example 12 was carried out using blends of both PCL and DICAP in 1:1 ratio under identical conditions. The emulsified polymer solution showed good film forming properties film post spray on sandy soil at room temperature.

Example 17: DMPA Polyol, MW 1934

(76) The synthesis procedure was identical to Example 1 with 25% HS. The amounts of precursors used are as follows:

(77) IPDI=11.21, DMPA=40.0 g, BMPA=0.759 g, Triethylamine=0.759, EDA=1.361 g, Deionized water=80.0 mL

(78) The emulsified polymer solution showed good film forming properties film post spray on sandy soil at room temperature.

Example 18: Water Flow Trial on Soil Stabilised with Composition of Example 1

(79) Simulating Stability of Soil in Flood Irrigation Furrows.

(80) Flood irrigation via furrowed beds has an inherent problem of uneven distribution of water which can lead to waste. If the soil were stabilised with CSIRO PU, this would in theory give a surface that would allow irrigation water to move more rapidly to the end of the furrow and allow water to be absorbed into the soil of the ridge (see FIG. 6) at a more even rate. This would improve water distribution in the crop root zone and reduce unwanted deep drainage.

(81) PVC plumbing tubes (15 cm diam.) used to simulate furrows. Tubes cut in half length ways (giving two test troughs) and silicone sealant baffles made onto inner surfaces (to stop soil slippage). Loam soil (Hanwood loam) packed into tubing (wet clay like) followed by sandy loamassemblies placed outdoors for a week in the rain to stabilise the soilto give cohesive strength to soil. One trough was sprayed with the composition of Example 12 with modifier. Both troughs were supported at one end to give a slope of 1 in 33 (approximately 3%). Water was supplied via a 1 L separation funnel with a tap to release water. Once released, the time of flow was measured and treated trough showed much reduce time 13 seconds compared to untreated trough which took 23 seconds.

Example 19: Pot Trials Using Example 1 with Different Viscosity Modifiers (Example 10 b, c and d)

(82) The composition corresponding to Example 10 (b, c and d) were prepared containing various viscosity modifiers as shown in Table 5 and were then sprayed onto soil surface in pot trials following standard pot trial method to measure cumulative moisture loss. The spraying quantity was about 5-6 g of the mixture and the results are summarised in FIG. 5

(83) TABLE-US-00005 TABLE 5 Trial Viscosity Amount reference modifier (% w/w) (a) alginate 2 (b) alginate 8 (c) Xanthan gum 2 (d) PAM 2

Example 20

(84) Field Trial

(85) Design and Layout

(86) Two crops were examined, rockmelon and sorgum and the rockmelon trial was conducted twice to confirm results.

(87) Each field trial involved a series of six 301.2 m beds. Three treatments were implemented for each triala control using standard irrigation practice with no polymer, a polymer treatment with the polymer composition of Example 12 applied at the rate of 1 kg/m.sup.2 on beds with irrigation reduced from the standard practice to provide 28% less water than the control, and a second control treatment with no polymer that received the same irrigation as the polymer treatment. All treatments were irrigated using drip irrigation with the volume of water applied measured by flow meters installed on the drip manifolds. The soil type was a loam with a surface bulk density of 1500 kg/m.sup.3. Particle size distribution was 22% Clay, 6% Silt, 62% fine sand and 10% course sand in the 0-0.1 m depth range. Configuration of the furrow and bed system is shown in FIG. 6. The bed or ridge was 120 cm wide with a drip irrigation tape a few centimetres below the soil surface. The mid furrow to mid furrow spacing was 1.83 m. Application of the polymer was applied to the total area of the bed for the polymer treatments.

(88) Results:

(89) TABLE-US-00006 TABLE 6 Example 6, Trial 1: Rockmelons 22-32% improvement in water use productivity Yield as a % Water use Increase in water Water applied Ave Yield of the productivity productivity over Treatment (ML/ha) (t/ha) control (t/ML) control Control 4.11 58.6 100% 14.26 (Full Irrigation) Polymer 2.98 56.0 96% 18.79 32% Control #2 2.98 45.8 78% 15.37 (Same water as polymer)

(90) TABLE-US-00007 TABLE 7 Example 6. Trial 2: Rockmelons 18-22% improvement in water use productivity Yield as a % Water use Increase in water Water applied Ave Yield of the productivity productivity over Treatment (ML/ha) (t/ha) control (t/ML) control Control 4.95 40.3 100% 8.14 (Full Irrigation) Polymer 3.52 35.1 87% 9.97 22% Control #2 3.52 29.7 74% 8.44 (Same water as polymer)

(91) TABLE-US-00008 TABLE 8 Example 12a Sorghum 15-34% improvement in water use productivity Yield as a % Water use Increase in water Water applied Ave Yield of the productivity productivity over Treatment (ML/ha) (t/ha) control (t/ML) control Control 3.05 24.7 100% 8.10 (Full Irrigation) Polymer 1.76 19.1 77% 10.85 34% Control #2 1.76 16.6 67% 9.43 (Same water as polymer)

Example 21

Properties of Polymer Formulation Example 1 and Example 12

(92) The mechanical properties of polymer examples are dependent upon specific formulation, HS content and polyol types. Example and 12 polymers showed UTS in the range of 8-15 MPa and elongation at break between 1100-1500%.

(93) The particle size and contact angle of the polymers of Examples 1 and 12 were determined and are reported in Tables 9 and 10.

(94) TABLE-US-00009 TABLE 9 Particle size Sample Code Particle size % Elongation Example 12 207 45 1852 31 Example 12b 205 55 1477 67 Example 12b 223 98 1321 104

(95) TABLE-US-00010 TABLE 10 Contact angle of cured films Contact angle Sample Code (e) Example 1 63 4 Example 10d with 60 11 xanthan gum (2%) Example 1 + SCMS 93 8

Example 22: Weed Control Using the Composition of Example 1

(96) The invention can be pigmented without adversely affecting the subsequent membrane. In this example black pigmented and unpigmented PU were trialed to suppress weed growth using lawn seed to simulate weeds. Hortico lawn seed with a 70% germination guarantee was used in Debco seed raising mix. The lawn seed, 3 grams, was evenly distributed across seed trays, 3327 cm in area, The base formulation used was Example 1 with SCMC (at 2.5% on wt of PU based on a 7.4% stock solution). Two spray formulations trialed (in triplicate): Example 1 with SCMC and Example 1/SCMC with 3% (wt/wt) black pigment acrylic paint and a doughnut shaped stencil was used to produce a non-treated section for watering from the top. An analysis of seed growth after 16 days assessed the total growth area of germinated lawn seeds as a percentage of total tray area for both spray treatments and pigmented PU spray showed significantly less weed growth 11.42.1 compared to unpigmented composition of Example 1, 20.90.8% and showed that black pigmented membrane acts as a weed growth suppressant when compared directly with an un-pigmented spray formulation.

Example 23: Biodegradation

(97) Biodegradation testing is carried out for films formed of the composition of Example 1 and the composition of Example 12 by adding the films to a respirometer containing soil and allowing to stand over a period of time during which the amount of carbon dioxide evolved is determined. The level of biodegradation is expressed in percent is determined by comparing the amount of carbon dioxide evolved with the theoretical amount.

(98) The test specimens used are in the form of approx. 150 micron thick film strips with the size 2 cm2 cm, Approximately 4.0 g of test materials (dry weight basis) are mixed with 200 g of soil (dry weight basis) and filled in the glass reactor. The glass reactors are placed in respirometric unit maintained at 28 C.2 C. for the test period. Test mixture (soil/soil and test material) in each bioreactor is continuously aerated with CO2 free humidified air and rehydrated as required. The amount of carbon dioxide evolved is measured at regular intervals (every 6 hours) using an infra-red CO2 analyser. At the end of the test, the residual materials are extracted from the soil and assessed for properties such as weight loss, MWs, level of oxidation, weight loss and % biodegradation. The water content of the soil is kept between 40-60% of the total water holding capacity, Cellulose is used as a positive reference material and 3 replicate are used in 3 different glass reactors. The test results up to 185 days are summarised in FIG. 7.

Example 24: Example 1 Prepared with PDMS X22-160AS (MW 928.24)/PPG MW 961.57

(99) The synthesis procedure was identical to Example 1. The amounts of precursors used are as follows:

(100) IPDI=10.374 g, PDMS=20.0.0 g, PPG=5.0 g, BMPA=0.498 g, Triethylamine=0.375 g, EDA=0.893 g. Deionised water=55.0 ml